In various control systems, such as, in pulse coded track circuits for railroad and mass and/or rapid transit operations, it is desirable to place at each wayside location where adjacent track sections are adjoining, a single central data processor unit (CPU) which provides control and/or data processing for a pair of an associated transmitter and receiver. The transmitter and receiver are connected to one of each track circuit, that is, to the rails of the corresponding track section. The central data processor unit (CPU) correlates the local conditions and establishes the pulse code transmitted in both directions through the track rails. Each of the processor units also decodes the received pulses to register the data picked up from the other end of the associated track section. In practice, the data processor unit is preferably a solid-state microprocessor device which is conventional and readily commercially available from any one of a number of electronics manufacturers. The CPU incorporates or is associated with the necessary memory, such as, programmable read only memory (PROM) devices which may be included therein. The CPU also receives inputs from the local devices which detect train presence and traffic conditions and records other data which is to be reported. The received data is registered in solid-state relays and is used to control the flow of traffic and to perform other functions. The processor unit also monitors the operation of the output register relays, the input signals from the wayside logic, and other functions through the use of monitoring devices and feedback signals. When these operational checks and monitoring devices determine that the system is functioning properly, and the results are in agreement and comparable to that which is expected, the CPU generates a signal having a predetermined special characteristic. When this signal is conveyed to the local power supply, a source of supply energy is available at that location for powering the system apparatus. The continued operation of the power supply is dependent upon the reception of the special check signal from the processor unit, and the power supply is inhibited in the absence of the check signal. Thus, the system is shut down at any given location when an indication of improper operation or failure of any of the system elements are indicated to assure vital safety or vitality of the system.